1. Field of the Invention
The present invention relates to a device for dispensing sensors for measuring the concentration of an analyte in a fluid sample (notably glucose in whole blood), and to a cartridge containing sensors for use in the device. The invention also provides a meter incorporating the dispensing device.
2. Description of the Prior Art
Diabetics regularly need to test samples of their blood to determine the levels of blood glucose. In one known type of test system, disposable sensors are used to test the blood. The sensors typically take the form of test strips which are provided with a reagent material that will react with blood glucose to produce an electrical signal. Conductive tracks on the test strip relay the electrical signal to a meter which displays the result. After a sample of blood has been applied to the test strip and the measurement has been taken, the test strip is disposed of. Examples of test devices with test strip dispensers are described in U.S. Pat. No. 5,660,791, and European Patent Application Numbers 0 732 590, 0 738 666, and 0 811 843.
A problem with test strips is that they have only a limited shelf life, and exposure of test strips to the atmosphere further reduces the shelf life.
In DE 196 39 226 A1 it is proposed to provide a test device with a cartridge that may have a plurality of chambers containing test strips, each of which chambers may be individually sealed to preserve the shelf life of the strips therein. A user removes the seal for each chamber when required, and a timing circuit may be activated either by the user or when the cartridge is pushed into the device. After a set time period has elapsed, an alarm or other indication reminds the user that the time period for using the strips has elapsed. WO 02/08753 describes a blood glucose meter which has test strips arranged in a plurality of stacks in a magazine. Each stack is individually sealed, and the stack's seal is broken automatically when the magazine moves to a location where a test member can be dispensed by means of a suitable pusher.
It has been proposed in WO 94/10558 to provide a stack of disposable sensors in a cylindrical housing, the stack being urged towards a test station to form a liquid-proof seal. In WO 02/18940 there is disclosed a blood glucose test meter in which a stack of test strips in a replaceable cartridge are sealed against a rotatable transport member which is adapted to receive a single test strip and rotatably transport the test strip while maintaining a seal around the cartridge.
A problem with such systems is that the sealing means may wear with repeated use and the quality of the seal may consequently be reduced.
U.S. Pat. No. 5,759,010 discloses a cartridge for dispensing slide test elements of the kind which have an opening for liquid access. The cartridge is provided with an internal cover plate which is biased to make a sealing contact with the opening so as to protect the inside of the opening from atmospheric moisture before the slide is dispensed. Such an arrangement is less desirable for test members in which the reagents are not located in an opening of a moisture-impermeable slide member because it is difficult to make a reliable seal around the reagents. Friction between the reagent layer and the plate may also tend to abrade the reagent layer.
It is an object of the present invention to provide an improved test device. It is a further object of the invention to provide an improved dispenser for sensors for use in measuring analyte concentration in an applied fluid.